A simple experiment suggests that using forest soil on a household doormat scan improve the mix of bacteria inside homes, potentially benefiting human health, according to new research from Finland.
Scientists from the Finnish Institute for Health and Welfare and the University of Eastern Finland found that adding small amounts of forest soil to an entryway rug changed the indoor microbiome, the collection of bacteria living in the home, making it more similar to natural outdoor environments.
Chief Researcher Martin Täubel said: ‘Applying forest soil onto a rug led to a clear rise in forest soil‑associated bacteria in the air. The effect was most pronounced at infant breathing height for the first two weeks after application, and the signal was also detectable in other areas of the home.’
The study focused on the idea that modern indoor environments, particularly in cities, often lack exposure to the diverse microbes found in nature. This reduced exposure has been linked to higher rates of conditions such as asthma and allergies.
To test whether this could be addressed, researchers introduced forest soil into five homes in Finland, while a sixth home acted as a control. Soil was added to a rug in the entrance area several times over a few months. The team then collected dust samples from different parts of the home, including areas at both adult and infant breathing height.
The results showed a noticeable increase in beneficial outdoor bacteria throughout the homes. In areas close to the rug, especially at lower heights where babies are more likely to be, bacterial diversity increased while human-associated bacteria decreased.
The researchers observed an increase in what they call the ‘farmhouse resembling microbiota index’ (FaRMI) which measures how closely house dust bacteria match those found in traditional farm homes, environments known to protect children against asthma and allergies.
After bringing forest soil indoors, researchers observed a small increase in FaRMI scores. This shift was comparable in scale to the protection associated with farm upbringing.
Senior author Pirkka Kirjavainen said: ‘It was promising to see that microbial exposure signatures associated with a lower asthma risk may be increased in urban homes with such a simple, low-cost intervention.’
While the findings are based on a small number of homes, the researchers say the approach could offer a practical way to improve indoor environments, particularly for young children who spend most of their time indoors.
The full research can be read here.
Photo: Andrew Neel
Leave a Reply